Telephone system



June 2, 1942- w. H. T. HOLDEN Erm. .2,284,870

TELEPHONE SYSTEM Filed Sept. 20, 1940 7 Sheets-Sheet l ATTORNEY June 2, 1942.- fw. H. Ar. HOLDEN rs1-A1. 2,234,870

TELEPHONE SYSTEM Filed Sept. 20. 1940 7 Sheets-Sheet 2 WHTHOLDEN By B F.' EW/5 A 7' TORNE V AKJDE /NVEA/Tom:

June 2,1942. w. H1. HQLDEN n 2,284,870

TELEPHONE SYSTEM- Filed Sept. 20, 19,40

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A T TORNE Y June 2, 1942 w. H. T. HoLDEN ETAL 2,284,370

TELEPHONE SYSTEM Filed Sept. 20, 1940 '7 Sheets-Sheet 4 a s t.

THOUSANDS RES/S TER A 7' TOR/VE V June 2, 1942- w. H. T. HOLDEN ET A1. 2,284,870

TELEPHONE SYSTEM Filed Sept. 20, 1940 7 Sheets-Sheet 5 WH THOLDEN /NVENTORSB E EW/5 A NORA/Ey June 2,

W. H. T. HOLDEN ETAL TELEPHONE SYSTEM Filed Sept. 20, 1940 '7 Sheets-Sheet 6 TENS AND WH r HOLDEN VVENTORS-. f EW/5 6.26. M

A TToR/VEV June 2, 1942.

W. H. HOLDEN ETAL TELEPHONE SYSTEM Filed Sept. 20, 1940 7 Sheets-Sheet '7 THU/ DEN /NVNTORSB BV @N150 Ok 4 bww A TTRNEV Patented June 2, 1942 l TELEPHONE SYSTEM William ll. T. Holden, Woodside, and Benjamin F.

Lewis, Bayside, N. Y., assignors to Bell '.lele-J phone Laboratories, Incorporated, New York, N. Y., a corporation of ANew York f ,Bussum JuL 101951 Application September 20. 1940' Semi N 357520 3 3 8 11 Claims.

This invention relates to telephone systems and more particularly to those systems in which the numerical indication of a calling line is automatically determined and made available.

It is well known that in certain types of telephone connections such as those, for instance. in which the calling line is extended automatically or otherwise to some remote station, it is sometimes necessary to ascertain the number of the calling station in order that charges for the call may be properly assessed to said station. Such connections are known as toll or long distance connections and in some types of automatic telephone systems in which the calling line is routed to its destination via the position of a recording operator where, after the number has been communicated to the operator by the calling subscriber, said number is veried over a socalled checking multiple. This verification is made by touching the tip of a checking cord to a pin in the checking multiple that is assigned to the given number and if the number as given by the calling party is correct, a tone circuit is completed over the checking cord which is heard in the operator's telephone set. On the other hand, if the number as given does not correspond to that of the pin to which the tip of the check- -ing cord is touched, the tone circuit is not completed, which fact indicates to the operator that the number given by the calling party does not correspond to that of the station from which he is calling and service may then be denied until the discrepancy is rectiiied.

In automatic telephone systems, it is desirable to have the identity of the calling station ascertained and transmitted automatically. to some point at which it may be recorded on settable registers for the visual display of the number, if the call is completed through an operators position, or for automatic recording if the information is to be utilized for operating printing or other recording devices responsive to the setting of the registers.

Our invention is principally concerned with the automatic identication of the callingl line number, and its principal feature is an arrangement of two main groups of electronic devices provided. with multicontrol elements which, when operated, produce two coordinate translations, 50-

one for each two digits of the line number, each of which may then be suitably resolved into a single translation for each digit. Similar identifying arrangements are utilized in the copending application of W, A. Rhodes Serial No. 357,-

518 and the copendlng application of W. A. Bascom et al. Serial No. 357,519 both filed on September 20, 1940.

Another lfeature of our invention is an arrangement of four auxiliary groups of electronic devices which, operating in conjunction with those of the two main groups, resolve the twodigit translations made by each main group ot devices into single-digit translations, one for each digit of the line number.

According to one embodiment of the invention as adapted to provide identication for each of the lines. of a ten thousand-line telephone oiiice and in which the electronic devices employed are of the so-called cold cathode gas-filled type well known in the art which break down and become conducting upon the application of a critical or breakdown potential to a control anode, we propose to use two main groups of one hundred such' cold cathode tubes each having one hundred control or starting anodes with each line to be identified connected to a starting anode in a tube of each group, and four auxiliary groups of ten cold cathode tubes each having ten starting anodes with each cathode of a main tube connected to a starting anode in a tube in each of two auxiliary groups. Upon the application of a distinct signaling voltage to any one of the lines, the two tubes in the main groups having one of their starting anodes connected to the line become conducting, and their conduction immediately activates each of the four tubes in the auxiliary groups having anodes connected to the cathodes of the two conducting tubes in the main groups. Since each of the auxiliary tubes bears a digital coordinate relation to its associated main tube, there is present in the four operated auxiliary tubes four distinct signals each of which designates a digit of the line. These signals may, of course, be received upon suitable registers from which the number may then be displayed or recorded by appropriate apparatus provided for the purpose.

A clearer conception of the scope and purpose of the invention may be obtained from the following description, taken in connection with the appended claims and attached drawings, in which- Fig. l shows a schematic layout of an automatic telephone line extension in atelephone system of a well-known type;

Fig. 2 shows, in part, one of the two main groups of. tubes; x

Fig. 3 shows, in part, the two auxiliary groups of tubes which are operatively associated with the main 'group of tubes shown in Fig, 2;

Fig. 4 shows the digit registers;

Fig. 5 shows, diagrammatically, theswitching circuit, the progress circuit and the printer;

Fig. 6 shows, in part, the other of the two main groups of tubes;

Fig. '7 shows, in part, the other two auxiliary groups of tubes which are operatively associated with the main group of tubes shown in Fig. 6; While Fig. 8 shows the manner in which Figs. 1 to 7,

inclusive, shouldA be arranged with respect to each other in order to disclose the invention.

Referring now, to the drawings, there are provided as indicated therein one hundred tubes, namely tubes 00 to 99, i clusive, for the thousands and hundreds digit designations of the various ones of the ten thousand lines in a telephone oilice and one hundred other tubes, namely, 600 to 699, inclusive, for the tens and units designations of said lines. Each tube in each group has one hundred and twoelements, namely, a main anode indicated by an arrowhead within the tube envelope and connected to conductor 242, a main cathode indicated by a long slender rectangle Within the tube envelope each connected to a source of negative potential, and one hundred starting an-odes indicated as short lines perpendicular to the cathode within the tube envelope. There are, therefore, twenty thousand main tube control anodes for the entire circuit.

Each line is provided with an identifying conductor, preferably an extension of its sleeve as, for instance, conductor H9, and this conductor is connected to a punching on the terminal assembly block TAB-I which is assigned to the line correlated to the identifying conductor. Thus in Figs. 1 and 2, conductor II9 is connected to terminal punching I9I9, and line A is assumed to have the same numerical designation as the punching. It will be observed that the terminal assembly block TAB-I is arranged in vertical sections of one hundred punchings to the section, there being, for a ten thousand line oice, one hundred such sections with each section allocated to a particular group of one hundred lines to the punchings of which are connected the sleeve extensions of the related lines, in the same manner as already described for line A (I9I9).

From the other side of the punchings of TAB-I extend two parallel conductors, one to a control anode in one of the one hundred tubes 00-99 and the other to a control anode in one of the one hundred tubes 60G-699 via a punching on terminal assembly block TAB-l1 which is identical in structure and arrangement to TAB-I. The tube in each group to which each of said conductors is connected depends, in the case of the iirst group of tubes 00-99, upon the thousands and hundreds numerical designation of the line and, in the case of the second group of tubes 60G-699, upon the tens and units designation of the line. Furthermore, since, as a matter of convenience, the one hundred control anodes in each of the tubes of both main groups are themselves numerically designated in consecutive order, the particular control anode in each tube to which each of the above conductors would be connected may be made to depend upon the identity between the numerical designation of the anode and the numerical designation of the two digits of the line number which are to be identiiied by a tube in the other main group.

Thus, punching I9I9 on TAB-I which, on one side is connected to conductor II9 isconnected on its other side to conductors 240 and 24I. The line I9I9 has a thousands-hundreds digit designation of I9" and since tube I9 is reserved for the identification of the numerical designation of the one hundred lines in the oilce bearing the thousands-hundreds designation I9 conductor 240 is extended to a control anode in tube I9 and, via resistance 244, particularly to the anode therein labeled I9; anode I9 having been selected because it bears the same numerical designation in the consecutive line-up of the hundred anodes of the tube as the tens-units designation of the line. In the same way, conductor 24| extends to terminal punching I9I9 in the terminal assembly block TAB-II and thence to a control \anode in tube II9, and particularly to control anode I9 therein via conductor 24I and resistance 644. Here again the particular anode in the tube selected for connection to conductor 24| may be determined as a matter of convenience by the thousands-hundreds designation of the line number which, in the case of line number I9I9 (line A) happens to be the same as the tensunits designation.

The identifying conductor of every line in each hundred line group of the one hundred such groups for a 10,000 line olce is thus similarly extended, via a resistance, to a control anode in the particular tube in the group of tubes 00-99 which is reserved for the thousands-hundreds identification of that group and, via another resistance, to a control anode in the particular tube in the group of tubes 600-699 which is reserved for the tens-units identification of that group. It is obvious that the operation of a tube in each group, each having one of its control anodes connected to the identifying conductor of a line through its extension from the punchings on terminal assembly blocks TAB-I and TAB-II may be used to operate auxiliary equipment and signaling apparatus that will identify the conductor and, therefore, the line.

Since the operation of a tube in the main group of tubes Uil-99 and the operation of another tube in the main group of tubes 60o-699 each identies a pair of digits of the line number, additional translations are necessary in order to trace back the identity of each of the four digits of which the line number is composed. To carry out these translations, two auxiliary groups of ten ten-control anode tubes are provided for each main group of tubes 00-99 and 600-699, one auxiliary group for each of the two digits decoded by a main group of tubes. These tubes are numbered 200 to 209, 2I0 to 2I9, inclusive, for the group of thousands-hundreds tubes 00-99, and 220 to 229, and 230 to 239, inclusive, for the group of tens-units tubes 600- 699. The cathodes of the tubes in each of the main groups are connected to negative battery through a high resistance, and conductors are brought from each of said cathodes to a start anode in a tube in each of the associated auxiliary group. The order of connection is ten cathodes from as many consecutively numbered tubes in a main group connected, respectively, to as many control anodes 'in a tube of one of the auxiliary groups, and each one of the same cathodes connected respectively to a control anode in each of the ten tubes in the other auxiliary group. The reason for this is that, in the case of the thousands-hundreds dilits. for example. the auxiliary group of tubes III-,2" inclusive is used to identify the different thousands digits of the line numbers, and inasmuch as there -will be a maximum of ten different numericalV in thesame tube of thev auxiliary group r200-.200

and to a control anode in each of the ten tubes of the other auxiliary` group 2I0--2I0the selection of the tube to whose control anode the cathode of `the main tube is to be connected being determined, of course, by the correspondence of the units digit of the numerical designation of the tube in the main group and that of the tube in the auxiliary group. In the same manner for thetens-units digits. The auxiliary group oi tubes 220-22'9, inclusive, is used to identify the different tens digit of the line numbers, and inasmuch as there will be a maximum of ten different numerical values of the units digit for each numerical value of the hundreds digit, the cathodes of the ten tubes which are to identify the same tens digit of --the line number for each different numerical value of the units digit are connected to as many control anodes in the same tube of the auxiliary group 220-229 and to a control anode in each of the ten tubes of the other auxiliary group 230-239, the selection of the tube to whose control anode the cathode of the main tube is to be connected being determined, of course, by the correspondence of the units digit of the numerical designation of the tube in the main group and that of the tube in the auxiliary group. The following table shows the distribution of connections.

Connections to tubes in new u tive auxihary 8" p5 groups oo 20o and 21o o1 20o and 211 o2 29o and 212 "2665121" '219 10 201 and 210 11 201 and 211 4 l'' `2i 91 m9 and 211 '99 'i' `2`1 60o 22o and 23o 601 22o and 231 226km 239 61o 221 and 23o 611 221 and 231 it 22i'1`1i1' '2st 62o 222 and 23o 19s 22`1' `2`s 699 229 ma 239 The anode voltage for all tubes is a superposed alternating current supplied by source 304' connected to the primary of transformer Ill the secondary of which is connected to negatively grounded battery 300 and-to conductor 242 which connects with all tube anodes. Preferably the source should be volts direct current plus 'l0 volts alternating current corresponding to a peak value of 200 volts. With 80 volts drop in the glow discharge of any of the tubes there will be a maximum of volts during slightly more' than the positive half cycle of anode voltage across the cathode resistances of the tubes in the main groups, so that there will he ample voltage to operate the control gaps of the tubes in the auxiliary groups. However. 'this is intended merely by way of illustration as it is obvious that the voltage values to be supplied cannot be fixed with any considerableaccuracy as they will depend upon the characteristics of the tubes used. y

The cathode of each tube in each of the two auxiliary groups of tubes 2id-239 is connected to a contact of multicontact relay 30| while the armature making with said contact is joined to a winding of a register relay. There is provided a register of ten relays for each of the digits to be identified, namely, a thousands register comprising relays ,THO-TH9, a hundreds register.

comprising relays H0-H9, a tens register comprising relays T0-T9 and a units register comprising relays U0U9. Each relay in each register is double wound with the right winding connected to an armature of said multicontact relay 30|, the connections to all relays being made consecutive in order to group the relays of each register with the cathodes of the tubes of the particular auxiliary group that `identifies the digit reserved for the register.

The register, relays are provided with a locking circuit to ground on the contacts of relay 505. They are also provided with two pairs of contacts which, when operated, apply ground to two of the five local conductors 400 -404, inclusive. in the appropriate combination called for by the following code to indicate the digit designated by the operated relay in the registers, and provided, further, with a third pair of contacts which ground conductor 408 for operating start relay 500 for a purpose set forth hereinafter. l

Tables of codes Conductors grounded Register relay operated Digit designated The groups of five local conductors 400-404 inclusive of each register are connected in consecutive order to the armatures of a relay 5i0, ill, SI2, and SIS, the make contacts of which extent to the magnets of any commercially available printer 506 via conductors'400-404. ThusA conductors 4001-4041 of the thousands register are connected to the armatures of relay 5|0; those of the hundreds register 4009-4042 are connected to the armatures of relay 51|; those of the tens register 4003-4043 to the armatures of relay SI2 and those of the units register 4004-4044 to the armatures of relay 5I3. These relays` are operated in a cyclical order by any suitable progress circuit 501 which first operates relay 5I0 to connect conductors 4001-4041 of the thousands register to the printer 505; then operates relays 5II, SI2 and 5I3 in the order given to connect, in succession, the signaling conductors of the other three registers operatively associated with the above relays. Inasmuch as each register will have one of its relays operated at the time of the cut-through to the printer, as will be shortly described, the two conductors in the register group which are grounded by said relay will cause the printer to operate and print the digit designated by said grounded conductors.

Having described the structural arrangement of our invention, its manner of operation when adapted to a specific type of telephone system will now be set forth in some detail.

In Fig. 1 is shown a schematic disclosure of the equipment at the originating omce of an automatic telephone system of the so-called stepby-step type wherein switching selectors, shown in the figure as 1st selector, 2nd selector, etc., are usuallysettable directly in response to dial pulses from an originating station to reach the terminals of a wanted station. In telephone connections involving the necessity of identifying the number of the calling station such as, for instance, long distance connections, the line is usually routed through a 3rd selector whence it is extended to its destination by well-known means. If, therefore, the switching train reaches the 3rd selector switch and this switch selectively connects itself to an outlet reserved for calls necessitating the verification of the calling line number, the line identification circuit comprehended by this invention is automatically connected to the trunk by any suitable means and proceeds with its operation of determining the number of the calling station.

The line identification circuit is used in ccmmon by a group of trunks and, in its operation is, of course, used only by one trunk at a time, an interval during which other trunks await their turn in any desired preferential order for connection therewith to obtain similar line identification service. common circuit is connected to a plurality of individual circuits on a lock-out basis are well known and numerous in the switching art. The connecting circuit shown in Fig. 1, therefore, is merely illustrative of a number of other and similar connecting circuits which might be used.

We may now assume that station A, identified by line number |9I9, initiates a call which requires line identification. When the various selectors have been selectively positioned to engage a trunk on the 3rd selector bank, line relay |00 of said selector operates over the line loop, causing thereby the operation of relay IOI over its lower contacts which, in turn, completes a cirsuit for relay |03 which extends from ground on the right contacts of relay IOI, right contacts of relay |05, winding of relay |03 to battery. Relay I03, upon operating, closes a path for relay |06 which extends from battery through the left outer contacts of relay |03, winding of relay |06, through the lower continuity contacts of relays IOSL-|06 which relays are identical with relay |06 but individual to each of the trunks having access to the identification circuit, to ground. If all the relays I06-|06I06" are normal, which Connector circuits by which a indicates that no trunk is locked in with the identification circuit, relay |00 will operate. On the other hand, if one of said relays is operated, indicating thereby that a trunk is locked in with the identification circuit, then the above circuit will not be completed and relay |06 will not operate, in which event the connection will wait until the circuit is established. Assuming, however, that all trunks are disconnected from the identification circuit, then relay I06 operates, locks Itself to ground through its lower front contacts and completes an obvious circuit for relay |01 which, upon operating, grounds conductor |08 and thereby causes the operation of relay 30|, closes through release conductor 09 to the winding of relay I 05 and completes a circuit for relay |04 which extends from ground through the upper inner contacts of relay |01, inner contacts of relay |03, winding of relay |04 to battery. Relay |04 operates and connects conductor |02 to the sleeve of the connection via the left contacts of relay |0| and thence to identifying conductor I I9 of the line A.

It will be observed that while relay |06 is operated, other trunks might cause their respective relays |06' to operate if they are located, electrically, to the right of relay |06. However, their operation will be ineffective since it will not be possible to operate their associated relay |01 inasmuch as the circuit of this relay is controlled over a chain connection to the left, .back to the upper back contacts of relay |06, which, being operated, opens the path of all other relays I01-I0'I except relay |01.

Conductor |02 which is now connected to conductor II9 via the sleeve of the selector train is connected to the secondary winding of transformer 303 which has its other terminal connected to positive battery 305. Inasmuch as alternating current source 304 is connected to the primary winding of transformer 303 and source 304 is connected to transformer 300, and since grounded negative battery 305 is connected to the secondary winding of transformer 303, a superimposed alternating potential is applied to conductor |02 (which is, of course, lower than the potential applied to the tube main anodes through transformer 300 in a conductor 242') and thereover via the sleeve of the selector train to conductor II9, punching |9I9 of terminal as-l sembly block TAB-I, conductor 240, resistance 244 to control anode I9 of tube I9 and, also, conductor 24|, punching I9I9 of terminal assembly block TAB-II, resistance 644 to control anode I9 of tube 6I 9. It will be observed that grounded positive battery through a resistance is connected to the cathode of each tube in the group 00-99 and 600-399. The difference of potential created by the superimposed positive voltage at anode I9 of tube I9 as traced thereto from the primary of transformer 303 and the negative resistance battery connected to the cathode of tube I9 is sufiieient to break down the control gap between the cathode and said anode. Similarly, the difference of potential between anode I9 and the cathode of tube 6|9 is sufcient to break down the control gap between the cathode and said anode. Both tubes I9 and 6I9, on being rendered conducting through the control gaps thereof, immediately break down in their respective main gaps inasmuch as positive superimposed potential through the secondary of transformer 300 is connected to the main anode of each of the tubes in the two main groups as already explained, and the difference of potentheir respective main gaps and become conduct-l ing therethrough.

As already explained, the main anode of each tube in the group of tubes -99 is connected to a control anode of a tube in each of its auxiliary groups of tubes 200-209 and 2|0-2l9. The same thing is true of the tubes in the group 600-699 in which the main anode of each tube is connected respectively, to a control anode of an appropriate tube in each of the two -auxiliary groups of tubes 220-229 and 230-239 as already described. In the case of tube I9, the main anode thereof is connected to controlanode |9 of tube 20| and to control anode 0| of tube 2|9; in case oi' tube 0|9, the main anode thereof is connected to control anode 09 of tube 22| and to control anode 0| of tube 239. However, since relay 30| is operated, the cathode of each tube in all four auxiliary groups is connected to negative battery through the operating winding of a relay in one of the numerical registers. Specifically, the cathode of each tube in the group 200-209 `is connected to negative battery through the winding of one of the relays of the thousands register, the cathode of each tube in group 2|0-2I9 is connected to battery through the winding. of one of the relays -in-the hundreds register, the cathode of each tube in group 220-229 is connected to battery through the winding of one of the relays in thetens register and the cathode of each tube in group 230-239 is connected to battery through the winding of a relay in the units register.

In tube the difference of potential between that on control anode |9 and that on' the cathode ofthe tube, applied thereto by grounded positive battery through the winding of relay THI, is

and start the operation of said progress circuit, which-may be of any suitable design, to complete circuits (not shown) whereby relays 5|0, 5| I, 5|2' and 5|3 are operated in the order given and .y whereby the succeeding relay is not operated un-f?l til the preceding one is released, and whereby the interval during which each of said relays is maintained in an operated position is suilicient to cause the performance of the registering or recording functions indicated below.

The apparatus supplied to receive the signal grounds applied to the four diierent `'groups of conductors 400-404- inclusive by the operation of a relay in each of the digits registers depends upon the kind of an indication of the calling number desired, as it is evident that any settable device adapted to record or register the application of grounds to said conductors and translate them into a visual, oral or recorded resignation of the calling number, will do. In the description of the invention herein given, merely by way of illustrating its operation, it is assumed that a permanent record of the calling line number is desired and that this record is to be a printed one which can be produced by any commercially available printer 506. When, therefore, relay 5|0 operates in preparation to record the thousands digit, an obvious circuit is closed for start relay 5|5 in the printer 506. Relay 5|5 operates to prepare the printer to receive the signal grounds on conductors 4021 and 4041 of the thousands register via the contacts of relay 5|0 and conductors 402-404, which grounds cause the operation of two corresponding printer vmagnets upon the operation of which the thousands digit I (according to the above table) is printed.

Following the release of relay 5|0 by the progress circuit, the start relay 5|5 also releases to-restore the printer. Upon the operation of relay'5l I, the Iive signaling conductors 4002-404: of the hundreds register are connected to the i printer via conductors 400-404 and another obsuflicient to break down the control gap of the tube thereby causing it to become conducting therethrough, and the flow of space current created thereby establishes a sufficient potential difference between the potential on the cathode of the tube and the superimposed alternating potential, applied to its main anode via conductor 202, through the secondary winding of transformer 300 as to cause the tube to ionize its main gap and produce a ow of current through the main anode and cathode paths. Since relay THI is included in this circuit path, said relay now operates over its right winding and locks over its left winding and contacts to ground on -the contacts of relay 505.

and lock over their respective left windings and` contacts to ground on the contacts of relay 505. It will be noted that the above relays, when operated, register the number |9|9 which, as above described, is the line number of the calling station A.

Relays THI, H9, TI and U9 all apply ground to the common conductor 408 which connects with the winding of the start relay 500 in the progress circuit, and causes said relay to operate l and 4022 of said lrundreds register.

vious circuit is completed for start relay 5|5 whereupon the printer is caused to repeat the` above operations for printing the hundreds digit 9 in response to ground upon conductors 40|2 Similar printing operations are repeated upon the operation of relays 5|2 and 5|3 in which the tens digit I and the units digit 9 are printed in response to ground on conductors 4023 and 4043 in the tens register and conductors 40|4 and 4024 in the units register. l

When the entire number has been printed, contacts 5|6 are momentarily closed in -the printer whereupon an obvious circuit is closed for slow-release relay 505.which operates to remove locking ground from the relays locked in the registers, causing said relays to release and restore the registers to normal. Relay 505 also `connects ground to conductor |09, completing thereby a circuit for relay |05 which extends from ground cn said conductor, top outercontacts of relay |01, winding of relay- |05 to battery. Relay .|05 operates, opens the circuit of relay |03 which releases, in turn releasing relay |04 which disconnects conductor |02 from the sleeve of the connection and applies ground thereto in order to provide a busy test'of the trunk for hunting 3rd selectors. Relay |03 further opens the circuit of relay |06 which, upon releasing, releases relay |01 which then releases relay 30| thereby disconnecting the cathodes of the tubes inthe auxiliary groups from the relays of the various registers and further restores the trunk connecting circuit to normal. Relay 505 is made slow release in order to insure sufficient time after the opening of contacts SIB to unlock the registers and to perform the above-described functions for restoring the trunk connector to normal. The release of relay 30| opens the cathode circuits of tubes 20|, 2I9, 22| and 239, respectively, causing said tubes to restore.

The removal of the signaling potentia/Lfrom conductor I I9 also causes its removal from the control anode lil of tube I9 and from control anode I9 of tube Ilil.A Thesev two tubesl with the controlling voltage removed, will now remain conducting only so long as the main anode voltage, applied through transformer 300, is on the positive half cycle of the voltage induced by source 304. When the voltage-reverses andnegative voltage is thus applied to the main anodes of these two tubes, they will cease to conduct and restore to normal. The identification circuit is now normal lin all its parts and may again be reseized for identification operations 4by other trunks.

One feature of this invention has not been mentioned before because it could not be understood without a description of the invention. It is the immunity of the identification circuit to false operations which may result from the presence of transients in the sleeve conductors of the various lines and, therefore, upon their respective identifying conductors. In telephone offices such transients, due to various causes, are always present and while they are not of sufficient magnitude to cause. the operation of electromagnetic apparatus connected thereto, may still be of sufllcient magnitude to break down the control gap of a tube in each main group and thereby produce in consequence the series of operations described above that would result in a line display even though the lines concerned would not be calling. In our invention, however, the tubes would operate if the main anode potential were on the positive half cycle of generator 304' at the time the transient occurs. But the tubes would quench immediately when the generator advanced to the negative half cycle and thus restore the circuit to normal before the tube operations could be registered in the relays of the digit registers.

While we have described the principle of our invention in connection with its specific application to a particular type of telephone system and to a specific arrangement of gas-filled devices, it is to be understood that various other applications and embodiments thereof may be made by those skilled in the art without departing from the spirit of the invention as defined Within the scope of the appended claims.

Whatis claimed is:

1. A calling line identification circuit for the lines of a telephone system comprising a plurality of electronic devices having control elements connected to said lines according to their numerical designation, and means responsive to the application of a potential to the control elements connected to one of said lines for operating the associated electron devices toindicate the identity of the line.

2. An identification circuit for the lines of a telephone system comprising in combination a plurality of electronic devices disposed coordinately relative to the lines of a telephone system whereby a potential applied to any one of said lines causes the operation of any two of said devices in coordinate relation to each other` to identify the line to which said potential was applied.

3. An identification circuit for the lines of a telephone system comprising in combination two groups of electronic devices disposed coordinately relative to the numerical designations of the lines of the system, means for applying a signaling potential through one of said. lines when calling to an electronic device in each group whereby said devices are rendered conducting, and other electronic devices responsive to the conduction of said devices for identifying the numerical desig" nation of said calling line.

4. A calling line identification circuit for the linesof a telephone system comprising two main groups of electronic devices having control electrodes connected to said lines, two auxiliary groups of electronic devices for each of said main groups of devices having control electrodes connected to the cathodes of the devices in the associated main group, means responsive to the application of a potential to the control electrodes of the devices in the two main groups for operating said devices whereby a potential is produced and applied to the control electrodes in the associated devices in the auxiliary groups, and means responsive to the application of said potential to said electrodes for operating the devices in the auxiliary groups to indicate the identity of the line.

5. A calling line identification circuit for the lines of a telephone system comprising in combination two main groups of electronic devices having control electrodes connected to said lines, two auxiliary groups of electronic devices for each of said main groups of devices having control electrodes connected to the cathodes of the devices in the associated main group, means responsive to the application of a potential to the control electrodes of the devices in the two main groups for operating said devices whereby a potential is produced and applied to the control electrodes in the associated devices in the auxiliary groups, and circuit closing means including settable registers available at said associated devices for operating said devices and setting said registers to indicate the identity of said line.

6. A calling line identification circuit for the lines of a telephone system comprising in combination two main groups of electronic devices having control electrodes connected to said lines, two auxiliary groups of electronic devices for each of said main groups of devices having control electrodes connected to the cathodes of the devices in the associated main group, means responsive to the application of 'a potential to the control electrodes of the line initiating a call for causing the associated electronic devices to become conducting, and means responsive to the operation of said devices for operating four of the devices in said two auxiliary groups for identifying the calling line to which said potential was applied.

7. An identication circuit for the lines of a telephone system comprising in combination an identifying conductor for each line, two groups of electronic devices disposed in coordinate pattern in relation to the numerical designation of each of the lines in the system, each electronic device in each group having a plurality of starting electrodes connected to as many line identifying conductors for identifying two digits of the associated line number, means for applying a signaling potential to the identifying conductor of one of said lines when calling and therethrough to the starting electrode in a device in each group connected thereto, wherebysaid devices are rendered conducting, and `other electronic devices responsive to the conduction of said devices for identifying the numerical designation of the line to whose identifying conductor the signaling potential Was applied,

8. An identification circuit for the'lines of a telephone system comprising in combination with an identifying conductor` for each line, a rst pair of electronic devices for a group of said lines, each of said devices having a starting electrode for each line in the group connected to the identifying conductor thereof, a second pair of electronic devices for each device in said rst pair of devices, each having a starting electrode connected to the cathode of a device in said :first pair, means responsive to the application of a signaling potential to the identifying conductor of a calling line in the group and, therethrough,

to the start electrodes of the first pair of devices connected to said conductor, for operating said pair of devices, means responsive to the operation of said first pair of devices for operating each of said second pair of devices, and means responsive to the operation ofeach of said second'pair of devices for identifying the conductor to which said signaling potential was applied.

9. A calling line identification circuit for la group of lines, each of said lines having a desigtential to the identifying conductor of a calling line in response to which the thermionic devices connected to said conductor are rendered conducting, and operative means included in the cathode circuit of said conducting thermionic devices for marking the designation of said calling line.

10. A calling line identification circuit for the lines of a telephone oiiice comprising a plurality of thermionic devices having control elements connected to said lines according to their numerical designation, each of said thermionic devices nation consisting of a plurality of symbols divida multiple of the number of lines in said group of lines, an identifying conductor for each line extending to a control element in each group of devices in accordance with the symbol identity of its associated line, means for connecting a pohaving a source of alternating potential applied to their respective anodes, settable registers. selectively connectable to said thermionic devices,

when operated, and means responsive to the application of a potential to the control elements connected to one of said lines for operating the associated thermionic devices whereby said registers are rendered settably responsive to said operated thermionic devices for recording the identity of the calling line. 11. A calling line identification circuit for the lines of a telephone oiice comprising a plurality of thermionic devices having control elements connected to said lines according to said numerical designation, each of said thermionc devices having aV source of alternating potential applied to their respective anodes, settable registers selectivelyconnectable to said thermionic devices. when operated, and means responsive to the application of a potential to the elements connected to one of said lines for operating the associated thermionic devices whereby said registers are not connected to said operated thermionic devices if said potential is not sustained at saidv elements during l the negative half cycles of said source of alternating potential connected to the main anodes of the operated thermionic. devices.

WILLIAM H. T. HOLDEN. BENJAMIN F. LEWIS. 

